In substrate processing chambers, process gases are introduced which are intended to affect the substrate to be processed in a predictable and repeatable way with a uniform effect across the surface of the substrate. In many processing chambers the process gas interacts with electrical and magnetic fields to form a plasma which facilitates and accelerates the reaction taking place at the substrate surface.
Vacuum processing chambers are connected to a vacuum pumping system which continuously evacuates the introduced process gas. In some vacuum chambers the vacuum pumping system connects to a pumping channel which wholly or partially surrounds the substrate being processed in an attempt to remove the process gas uniformly from around the substrate. In other configurations a simple pipe nozzle in the side of the processing chamber provides a single vacuum port for the whole processing chamber. The gas flowing from the gas inlet openings to the single vacuum port creates a gas flow pattern within the chamber. Flow patterns/or flow regimes are designed so that they flow across the substrate.
The goal in processing a substrate is that the process gas promote deposit on or etch of each unit area of the substrate surface equally. To accomplish this objective, the molecules of the processing gas must be directed in such a manner that their reactants, whether for deposition or etching, contact the substrate surface generally equally in each unit area of the substrate surface. A non-uniform gas flow pattern can create undesirable variations in surface film thickness, which may result in defects. To prevent such defects substrate processing times are adjusted so that the range of predicted film variations due to non-uniform gas flow patterns are taken into account to assure that film coverage or etching is complete at each film layer.
In each new processing chamber and for each new process condition, the process gas flow pattern is subject to change and evaluation by extensive empirical testing until optimum process parameters and process gas distribution manifold configurations are identified. A single gas distribution nozzle pattern is rarely optimal for more than a small range of process conditions.
In instances where plasma is used to facilitate and/or accelerate the deposition or etch process taking place in processing chamber, the material deposited tends to deposit on or the etch gas etches away the processing chamber surfaces exposed to the plasma, including the surface opening(s) through which the process gas is introduced into the process chamber. Metal pieces are generally particularly susceptible to plasma corrosion. Since the openings introducing process gas into the processing chamber act as orifices/restrictions to limit the process gas flow into the chamber, a change in the opening size, due to deposited material or enlargement due to etching, affects the gas flow rate and the gas flow pattern across a substrate being processed. Cleaning and/or replacement of the gas flow passages into the processing chamber needs to take place regularly so that variations in substrate processing are not so great as to cause defects when the changes in size of the gas passage opening adversely affect the gas flow pattern and the uniformity of film thickness on the substrate. Variations in film thickness of a substrate being processed must be minimized to optimize the quality of substrate processing. Further, if gas nozzles become dirty they may suddenly release and spray particles around the chamber which can cause defects in the substrate.
To minimize variations in flow due to deposits in or erosion of the gas flow passages, the gas supply/distribution manifold needs to be constructed to provide easy access to gas flow passages, especially those openings leading directly into the processing chamber and facing the area in the processing chamber where plasma will be present for easy cleaning and/or replacement of components. Monitoring and cleaning or replacement of worn components will avoid noticeable variations in the gas flow that might alter the predetermined optimum gas flow pattern. Variations in the gas flow pattern must be minimized to provide increased uniformity in the deposition or etching of a substrate surface in the processing chamber. Reducing and simplifying the number of steps and the time needed to clean and/or replace those structures in the gas feed system which are subject to deposition and/or etching by virtue of their facing the plasma in the processing chamber would decrease the down time of the system, increase the process chamber throughput, and promote process uniformity across the wafer.